I disagree with that sentiment. Even before it was retconned that he was their father, he was still cast as something of a father-figure to them and their relationship with him was a pretty big deal for both characters.

And I disagree with that. Maybe later on as they had already decided to go with the retcon, and even then I don't think so, but not before then. They were being lied to and blackmailed into joining the Brotherhood of Evil Mutants, and were saved from being hurt by people just like Magneto saves every mutant. They left when they realized Magneto was really the bad guy. And that's still irrelevant to me, because up until before they gain their powers he has no role in their lives at all. The people who they are in A2 can be the same as they were from the comics because Magneto had no role in who they became.